Total Hip Arthroplasty (THA) is a common surgical procedure in orthopaedic surgery which can be associated with perioperative blood loss and severe postoperative pain. Adequate pain management is very important to achieve early mobilisation in order to avoid immobility-induced complications. Non steroidal antirheumatic agents (NSAIDs) as selective Cox-2 inhibitors are commonly used in the management of postoperative pain. There exist non-selective and selective Cox-inihibitors. Non-selective NSAIDs block the systhesis of prostagandins by the two iso-enzymes of the cyclooxygenase, Cox-1 and Cox-2. For this reason the bleeding risk after operations (e.g.tonsillectomy) is increased.